#!/usr/bin/perl -w
use strict;
use XML::Twig;


my $t= XML::Twig->new( twig_handlers => { _all_ => sub { $_->insert( sort values %{$_->atts});
                                                         $_->del_atts;
                                                       },
                                        },
                     )
                ->parse( \*DATA)
                ->print;

__DATA__
<open1 type="head1">
This is test. <em type="italic">emp</em> this <i>emp</i>  is <em type="bold">emp</em> test.
</open1>